Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.49	3.128%	$103.6333	$103.63	$103.65	$103.60
Purchase #2	$213.51	13.855%	$243.0918	$243.09	$243.10	$243.10
Purchase #3	$37.44	4.506%	$39.127	$39.13	$39.15	$39.10
Purchase #4	$64.52	9.873%	$70.8901	$70.89	$70.90	$70.90
Purchase #5	$14.38	10.769%	$15.9286	$15.93	$15.95	$15.90
Purchase #6	$131.53	8.843%	$143.1612	$143.16	$143.15	$143.20
Purchase #7	$137.50	6.799%	$146.8486	$146.85	$146.85	$146.80
7 purchase totals =	$699.37		$762.6806	$762.68	$762.75	$762.60